High strength, combustion-resistant, tube-extrudable aircraft-grade magnesium alloy

ABSTRACT

Embodiments of the invention include magnesium-based alloys especially adapted for extrudable aerospace grade applications. Alloys of the invention provide excellent combinations of mechanical properties, good extrudability in hollow forms, and resistance to combustion.

FIELD OF THE INVENTION

The present invention relates to high strength wrought magnesium alloysdesigned for aerospace applications. More specifically, the inventionincludes a Mg—Al—Zn—Mn—Ca—Y alloy, which is non-flammable and improveson extrudability and mechanical properties of conventional alloys. Theinvention also includes a method of making the alloy in a selectedmanufacturing process.

BACKGROUND OF THE INVENTION

In automotive and aerospace applications, lightweight materials areincreasingly used to replace heavy structural elements in order toincrease vehicle fuel efficiency. Titanium and aluminum are commonmaterial choices for reducing weight in structural applications, butmagnesium alloys are superior because they have the lowest density ofany structural metal and can achieve higher specific strengths (strengthto weight ratio) than other metals. However, there are significantdesign challenges which have prevented the implementation of acommercial alloy in aerospace applications.

There are several distinct challenges for magnesium alloys in aerospaceapplications. The main challenges include strength, workability, cost,and flammability. Strength requirements are straightforward; becausemagnesium competes mainly with higher strength aluminum and titaniumalloys, it must have high strength in order to substitute into anyexisting application. Workability and cost requirements are interrelatedand are dependent on alloy strengths. Most aerospace components havecomplex shapes with high strength or stiffness to weight ratios. Theseshape and strength/stiffness requirements, as well as differing wallthicknesses, all necessitate a highly workable alloy. Alloys withmoderate or low workability must be extruded at higher temperatures andlower speeds in order to make these complex shapes; this translates intohigh process costs. While not a consideration for other structuralmetals, magnesium alloys in commercial aerospace applications must alsobe nonflammable or self-extinguishing if ignited. Flammabilityresistance is required due to stringent safety regulations that mandateaggressive testing of magnesium alloys. All of these criteria must bemet in order for a magnesium extrusion alloy to be commercially viablefor the aerospace industry.

Individually, solutions exist for each of these challenges, but thesolutions are often incompatible or contradictory. For example, highalloying content of aluminum or zinc results in high strength, butreduces workability, as visible in commercial alloy AZ80, which is notextrudable in tube, and alloy ZK60, which is extrudable only very slowlyin any form factor. Calcium additions contribute to the flammabilityresistance of magnesium alloys, but they can also lower the strength,ductility, and/or toughness of the alloy. Significant additions ofyttrium and rare earth elements, as in alloy WE43, result in highstrengths and flammability resistance; however, such additions aredetrimental to workability and are cost-prohibitive. Lean alloys thathave little alloying content are easily workable and inexpensive, butthey fail all other design criteria. There remains a need for an alloywhich satisfies all essential design criteria: good mechanicalproperties, combustion resistance, and workability and low cost.

SUMMARY OF THE INVENTION

The present invention relates to magnesium alloys that are ideallysuited for applications in aerospace and automotive applications. Thealloys have good flammability resistance, and extrudability, as well assuperior as-fabricated mechanical properties to similar conventionalalloys.

The present invention provides for embodiments that incorporatedifferent ranges of alloying content which gives flexibility and a goodbalance of options for processing and mechanical properties.

According to one aspect of the invention, the alloys may lie incomposition ranges (by weight) of between about 7.0 to 11.0% aluminum,0.1 to 0.8% zinc, 0.15 to 0.65% manganese, 0.6 to 1.5% calcium, and 0.05to 0.6% yttrium with remainder of magnesium and incidental orunavoidable impurities.

According to one preferred embodiment of the invention, it may beconsidered a magnesium-based extrusion alloy composition comprising, byweight: 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca,0.05%-0.6% Y and a balance of Mg and unavoidable impurities.

There are a number of additional optional features of the firstpreferred embodiment. One optional feature is wherein a content of saidMn is between about 0.15 wt % to 0.3 wt % of said alloy.

Another optional feature is wherein a content of said Zn is betweenabout 0.1 wt % to 0.35 wt % of said alloy.

Another optional feature is wherein a content of said Zn is betweenabout 0.4 wt % to 0.6 wt % of said alloy.

Another optional feature is wherein a content of said Al is betweenabout 8.3 wt % to 10 wt % of said alloy.

Another optional feature is wherein a content of said Ca and Y isbetween about 0.75 wt % to 1.5 wt % of said alloy.

Another optional feature is wherein a total combined content of said Al,Ca, and Y does not exceed 11 wt % of said alloy.

Another optional feature is wherein said Ca and said Y are provided inintermetallic compounds.

Another optional feature is wherein said intermetallic compounds of Caand Y comprise Mg—Al—Ca compounds and Al—Mn—Y compounds, respectively.

Another optional feature is wherein said Mg—Al—Ca intermetallic compoundcomprises up of up to 57 wt % Al and up to 43 wt % Ca.

Another optional feature is wherein said Al—Mn—Y intermetallic compoundcomprises 40 wt % Al, 40 wt % Mn and 20 wt % Y.

Another optional feature is wherein said Ca and Y intermetalliccompounds contribute to flammability resistance of wrought products madefrom said alloy.

Another optional feature is wherein said alloy comprises Ca in the formof intermetallic particles; said particles having an average diameter ofabout less than 1 μm and finely distributed within said alloy.

Another optional feature is wherein said intermetallic particles areformed in a wrought process, including extrusion, rolling, or forging.

Another optional feature is wherein when said alloy is provided in amatrix phase, particles making up said alloy have an average diameter ofabout 10 μm or less.

Another optional feature is wherein said alloy comprises Caintermetallic particles and said particles make up between about 1.0% to5.0% of said alloy by volume.

Another optional feature is wherein said alloy has a tensile yieldstrength of at least 180 MPa and an ultimate tensile strength of atleast 270 MPa.

Yet another optional feature is wherein said forged or drawn alloy has atensile yield strength of at least 170 MPa, an ultimate tensile strengthof at least 280 MPa and an elongation of at least 7% in tube forms.

According to another preferred embodiment of the invention, it may beconsidered a method of making a product made from a magnesium-basedalloy composition comprising the steps of: providing magnesium-basedalloy composition comprising, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn,0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg andunavoidable impurities; subjecting said alloy to extrusion to produce anextruded alloy; or subjecting said alloy to rolling to produce a rolledalloy; or subjecting said alloy to forging to produce a forged alloy.

One optional feature of the method is wherein said extrusion stepcomprises extruding said alloy into seamless tubes via extrusion of ahollow billet around a mandrel, or into structural tubes via extrusionof solid billets using porthole dies which split metal flow andsubsequently merge the metal around a mandrel to form a hollow shape.

Another optional feature of the method is wherein said extruded alloyhas a tensile yield strength of at least 180 MPa and an ultimate tensilestrength of at least 270 MPa.

Yet another optional feature of the method is wherein said extrudedalloy has a tensile yield strength of at least 170 MPa, an ultimatetensile strength of at least 280 MPa and an elongation of at least 7% intube forms.

According to yet another preferred embodiment of the invention, it maybe considered a magnesium-based extrusion alloy composition consistingessentially of, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn,0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg and unavoidableimpurities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph of an alloy of the invention showing an1280 μm by 960 μm area of the alloy in a cast condition;

FIG. 2 is an electron micrograph of another alloy of the inventionshowing a 256 μm by 192 μm area of the alloy in an extruded condition;and

FIG. 3 shows photographs of extruded forms of the alloys.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an electron micrograph example of the alloy 10 of presentinvention in an as-cast state. FIG. 1 more specifically shows prominentfeatures of the microstructure including a magnesium matrix phase 12which makes up most of the microstructure and which contains dissolvedaluminum and an aluminum and calcium rich phase 14 that is present ininterdendritic spaces left by the magnesium matrix phase. The grainboundaries of the magnesium matrix are not well defined but have sizeswell over 100 μm. A 100 μm scale is provided in the figure for sizecomparison. The aluminum and calcium rich phase is contiguous along someof these boundaries and exists in unbroken linear segments up to 100 μmlong. The microstructure also contains blocky Al—Mn—Y particles 16.

FIG. 2 shows another electron micrograph example of the alloy 10 of thepresent invention in an as-extruded state. The microstructure consistsmainly of relatively fine Mg grains 18 having an average diameter of 8.9μm. A 500 μm scale is provided in the figure for size comparison. Themicrostructure also contains stringers of Ca-rich particles 20, whichhave been broken up and distributed throughout the microstructure by theextrusion process. The Ca-rich particles 20 make up approximately 3.9%(by area) of the total microstructure and have an average diameter of0.48 μm. The thorough distribution of these Ca-rich particles helps pingrain boundaries of the matrix phase during and after extrusion, keepingthe material's grain size small and contributing to the material's highstrength. The small size of the Ca-rich particles makes them less likelyto be a failure initiation site, meaning that there should be littledetriment to the material's ductility. The microstructure also containscoarse or blocky Al—Mn—Y particles 22 that have not been broken up bythe extrusion process and which do not serve to refine themicrostructure.

FIG. 3 shows a photograph of examples of extrusions of the presentinvention. The present invention is extrudable in both tube form 24 andbar form 26. Other high strength magnesium alloys with aluminum as theprincipal alloying element are not typically extrudable in tube forms.

As mentioned, according to one preferred embodiment, the inventionincludes a magnesium alloy with alloying content, in weight percent,between 7.0% and 11.0% aluminum, between 0.1% and 0.8% zinc, between0.15% and 0.65% manganese, between 0.6% and 1.5% calcium, and between0.05% and 0.6% yttrium.

According to another feature of the invention, it includes an alloyingaddition of Mn between about 0.15% and 0.65% by weight. Furthermore, itis preferable that the alloy contain between 0.15% and 0.3% Mn byweight. Manganese is added to Mg—Al alloys to increase corrosionresistance by reducing the Fe impurity levels in the melt during primaryprocessing; dissolved Fe content is very detrimental to Mg alloys'corrosion properties. In the present invention, this preferred rangeresults in low Fe impurity levels and also low amounts of Al—Mnprecipitates in the metal, contributing to the invention's superiorworkability.

According to yet another feature of the invention, it may include analloying addition of Zn between about 0.1% and 0.8% by weight. In oneembodiment, it is preferable that the alloy contain about 0.4% to 0.6%Zn. Zinc is added to the alloy for solid solution strengthening. In thispreferred Zn content range, there is some effect of strengthening, butthe Zn content is low enough to allow extrusion at moderate speeds andtemperatures. In another embodiment of the present invention, it isinstead preferable for the Zn content to be between 0.1% and 0.35% ofthe alloy by weight. This amount of Zn will allow some solid solutionstrengthening but will allow a slightly higher extrusion temperature,allowing the invention to be extruded at higher speeds.

According to yet another feature of the invention, it may include a Caaddition of between about 0.6 wt. % and 1.5 wt. % and a Y addition ofbetween 0.05 wt. % and 0.6 wt. %. This combined Ca and Y additionimparts flammability resistance to the invention. The most obviousbenefit is imparting flammability resistance in the final product, butequally important is the effect of flammability resistance duringprocessing. For the present invention, billets of raw material can besafely preheated to higher temperatures than conventional alloys and cansubsequently be extruded at higher temperatures. Higher workingtemperatures increase the workability of the present invention and allowit to be extruded into tubes and complicated shapes; similar tubes andshapes would be impossible to extrude in conventional high strengthMg—Al alloys.

According to yet another aspect of the invention, it may include a Caaddition resulting in the formation of Mg—Al—Ca intermetallic compoundswhich are broken up and finely dispersed by a wrought process. Theseparticles contribute to grain refinement during extrusion and helpmitigate grain growth immediately after extrusion or during subsequentheat treatment. It is preferred that the invention contain approximately1.0% to 5.0% (by volume) of such particles and that such particles havean average diameter of less than 1μm. Furthermore, it is preferred thatthe Mg matrix grains of the invention have an average diameter of lessthan about 10 μm resulting from the finely distributed intermetalliccompound content of the invention.

According to another aspect of the invention, it is preferred thatcomponents of the present invention are produced via extrusion. Anyother wrought process which subjects a material to significant sheardeformation, and which is capable of breaking up the aforementionedCa-containing intermetallic particles of the present invention, may alsobe used, including forging or rolling. The extrusion processaccomplishes this by using a hydraulic ram to force a billet through anorifice in the desired shape. The rolling process accomplishes this byusing a set of flat rollers to impose successive thickness reduction ofa plate or sheet or by using a set of shaped rollers to do the same forsimple shapes. The forging process accomplishes this by slowlycompressing or rapidly impacting a material one or more times with ahammer, die, or set of progressive dies.

According to yet another aspect of the invention, it may include a totalamount of Ca and Y alloying addition be between about 0.75% and 1.5% ofthe alloy by weight. This amount of Ca and Y alloying addition has beenfound to give the present invention a favorable volume fraction ofCa-containing and Y-containing precipitates. This is sufficient forgrain refinement purposes but will not contribute too much tobrittleness. Further, it is preferred that the alloying content of Y beat the low end of the above prescribed 0.05 wt %-0.5 wt. % range, inorder to minimize costs associated with rare earth alloying additions.

As set forth, a preferred embodiment of the invention provides an Alalloying addition of about 7.0 wt. % to 11.0 wt. %. This alloyingaddition may be more preferably an Al content of between about 8.3% and10% of the alloy by weight. Such an amount of Al content has been foundto give the present invention good mechanical properties from solidsolution strengthening, while still remaining low enough in totalalloying content so that the alloy can be easily extruded. Such anamount of Al content also gives the present invention a Mg₁₇Al₁₂ solvusvery similar to conventional high strength Mg—Al alloys, meaning thatthe present invention has a potential for age hardening in a similarmanner as conventional high strength Mg—Al alloys.

According to yet another aspect of the invention, it may include a totalamount of Al, Ca, and Y alloying additions to not exceed about 11 wt %of the total alloy. This maximum ensures that the material will notbecome brittle and will maintain workability at safe workingtemperatures.

Several examples of the present invention demonstrate improvedproperties over existing commercial alloys. The material examples wereproduced by casting ingots and subsequent extrusion. Casting consistedof a fluxed process in a steel crucible, using high purity magnesium,aluminum, and zinc metals, manganese chloride, and magnesium-calcium andmagnesium-yttrium master alloys as input materials. Molten alloys weregravity cast into permanent steel molds. The chemistry of each examplealloy was verified via optical emission spectroscopy (OES). Alloyexamples are listed in Table 1. Comparative Example 1 and ComparativeExample 2 are commercial alloys AZ61 and AZ80 respectively. For thesematerials, the compositions listed in Table 1 are the nominalcompositions for those alloys instead (not verified by OES), and theywere produced using a larger scale direct chill casting process.

TABLE 1 Alloy Chemistries Composition, wt. % Alloy Al Ca Mn Y Zn Example1 7.45 1.34 0.15 0.13 0.52 Example 2 8.34 1.41 0.17 0.14 0.62 Example 38.56 0.79 0.22 0.07 0.63 Example 4 9.42 0.71 0.23 0.09 0.65 Example 59.98 0.66 0.18 0.08 0.64 Example 6 8.69 0.82 0.15 0.41 0.6 Example 7 9.20.8 0.16 0.36 0.62 Example 8 9.97 0.83 0.24 0.56 0.6 Example 9 9.23 1.010.19 0.11 0.65 Example 10 9.54 0.63 0.15 0.42 0.65 Comparative 6.5 00.33 0 0.95 Example 1 Comparative 8.5 0 0.33 0 0.50 Example 2

Billets were scalped to two final diameters and sectioned to length forextrusion. Billets were preheated in a furnace for up to two hours priorto extrusion. Extrusion was carried out on a 500-ton extrusion presswith three die geometries, which correlated to two extrusion profiles.Combinations of billet and die configurations are listed in Table 2.Often, a flat die for a round rod with an extrusion ratio of 25 is usedto benchmark extrusion speeds. More complicated shapes and higherreduction ratios are more difficult to extrude, especially for portholedies and hollow shapes, where higher pressure is required to overcomefriction with greater surface area in the die. The choice of diesprovided in this example is closer to an industrial setting, and itallows for demonstration of the present invention's superiorextrudability in both bar and tube form.

TABLE 2 Extrusion geometries. Reduction ratio Billet Extrudate(extrusion diameter Die type geometry ratio) Alloys used 3.18″ Portholetube 30 mm outer 29.28 Examples 3 - die. diameter, 2 mm 10 wallthickness. 4.16″ Porthole tube 30 mm outer 49.86 Examples 1 - die.diameter, 2 mm 2, Comp. wall thickness. Example 1 4.16″ Flat die. 1.5″by 0.25″ cross 36.25 All alloys section rectangular bar.

During extrusion, temperatures of the billet, die, and container varied.Temperatures were continually adjusted during experimentation in orderto maximize extrusion speed for all example alloys. All temperatureswere between 275° C. and 480° C. (527° F.-896° F.), but processtemperatures were generally between 370° C. and 480° C. (698° F.-896°F.). Using these conditions and the die geometries in Table 2, theextrusion speeds and mechanical properties of extrudates are listed forbar form in Table 3 and are listed for tube form in Table 4.

TABLE 3 Extrusion and mechanical properties of example alloys in barform. Maximum defect- Tensile Ultimate Elongation free extrusion YieldTensile after speed (feet per Strength Strength fracture Alloy minute)(MPa) (MPa) (%) Example 1 11.1 188 298 12.72 Example 2 8.2 194 274 5.58Example 3 8.2 190 301 12.05 Example 4 8.2 203 307 10.29 Example 5 5.7217 290 4.16 Example 6 7.3 187 290 7.88 Example 7 6.9 197 276 5.81Example 8 6.9 208 306 9.46 Example 9 5.4 201 300 8.66 Example 10 5.1 203299 8.47 Comparative 6 165 275 9 Example 1 Comparative 7 195 295 8Example 2

TABLE 4 Extrusion and mechanical properties of example alloys in tubeform. Maximum defect- Tensile Ultimate Elongation free extrusion YieldTensile after speed (feet per Strength Strength fracture Alloy minute)(MPa) (MPa) (%) Example 1 7 199 280 7.79 Example 2 5.6 194 319 9.94Example 3 6.1 187 306 9.16 Example 4 5.8 188 308 7.44 Example 5 5.1 170280 6.06 Example 6 6.1 171 295 9.21 Example 7 5.6 173 298 8.56 Example 85.3 192 295 6.15 Example 9 5.6 191 302 8.34 Example 10 5.6 183 296 7.36Comparative 6 110 250 7 Example 1 Comparative N/A N/A N/A N/A Example 2

For all Examples of the present invention, strengths in Tables 3 and 4were measured using the testing procedures described in ASTM B557-15.Tensile properties were measured in the extrusion direction of thematerial using samples that had 2″ gage lengths, 0.50″ widths, andnominal thicknesses of the material (listed in Table 2). Tensile YieldStrength was determined via the offset method detailed in ASTM B557-15section 7.1.6, and it generally refers to the tensile stress that can beimposed on the material before it will permanently deform. UltimateTensile Strength is calculated as the maximum force the specimen willwithstand, divided by its initial cross-sectional area. Elongation afterfracture was determined per the method listed in ASTM B557-15 section7.8.1, and it generally refers to the percent increase in the specimen'sgage length after tension testing. For the commercial alloys AZ61 andAZ80 (Comparative Example 1 and Comparative Example 2, respectively),reference mechanical properties are taken from the relevant alloyspecifications in ASTM B107.

Values for mechanical properties listed in Tables 3 and 4 are averagesof test sets of up to 12 samples, with any sample discarded which hadmeasurements at least 3 scaled median absolute deviations (MAD) lowerthan the median (about 2 standard deviations lower than the median), inorder to prevent skewing the results due to a defect in the sample.Commercial alloy AZ80 (Comparative Example 2) is widely known to not beextrudable in tube or other hollow forms; as such, properties are notgiven for Comparative Example 2 in Table 4.

Tables 3 and 4 demonstrate that the present invention has excellentas-fabricated mechanical properties relative to commercial alloys. AllExamples well exceed the yield strength of AZ61 (Comparative Example 1)in both tube and bar form. All Examples are also on par with AZ80(Comparative Example 2) yield strength in bar form, with most Examplesexceeding it. With the exception of Example 2, all Examples exceed theultimate tensile strength (UTS) of AZ61 in bar form, with most Exampleson par with or exceeding the UTS of AZ80. All Examples well exceed theUTS of AZ61 in tube form. In bar form, most Examples have elongation onpar with or exceeding AZ80, with some examples exceeding the elongationof AZ61. In tube form, most Examples exceed the elongation of AZ61.

Tables 3 and 4 also demonstrate that the present alloys have excellentworkability relative to commercial alloys. Most Examples have extrusionspeeds on par with that of AZ61 (Comparative Example 1) or AZ80(Comparative Example 2) in bar form. Some Examples significantly exceedthese reference speeds, with Example 1 having an extrusion speed nearlydouble that of AZ61 in bar form. Unlike AZ80, all Examples areextrudable in tube form. In tube form, most Examples are on par with theextrusion speed of AZ61, with some Examples exceeding AZ61 speeds. Inaddition to simply being extrudable in tube form, it is especiallysignificant that the present invention is able to maintain mechanicalproperties on par with AZ80, while being extrudable in tube form.

Selected alloys were tested for flammability by a third party, pursuantto the FAA Aircraft Materials Fire Test Handbook, Chapter 25 (Oil BurnerFlammability Test for Magnesium Alloy Seat Structure). Test results aresummarized in Table 5.

TABLE 5 Flammability Test Results Alloy Test Result Example 1 Pass - noburning Example 2 Not tested Example 3 Pass - no burning Example 4Pass - no burning Example 5 Not tested Example 6 Not tested Example 7Not tested Example 8 Pass - no burning Example 9 Pass - no burningExample 10 Pass - no burning

Comparative Example alloys 1 and 2 were not tested in this mannerbecause they are known to be flammable and are known not to beself-extinguishing. The Example materials which were tested all pass theflammability test requirements and demonstrate clear superiority overconventional alloys, especially for applications which requireflammability resistance. Referring to Table 1, the alloys which weretested reflect alloys with a combination of the highest and lowest Caand Y content, which gives good confidence that all combinations of thepresent invention have significant flammability resistance.

The alloys described herein are robust and may be produced via manyproduction methods. The preferred production method for Mg alloysaccording to the present work is direct chill (DC) casting followed byextrusion, but it is not intended that the present invention be limitedto a specific process. Rather the process may be designed for severalother casting and wrought processes not mentioned in detail. Suchcasting methods include but are not limited to sand casting, gravity diecasting, tilt casting, low pressure die casting, high pressure diecasting, strip casting, continuous casting, squeeze casting, centrifugalcasting, thixomolding, and rheocasting. Such wrought processing methodsinclude but are not limited to extrusion, rolling, and forging.

1. A magnesium-based extrusion alloy composition comprising, by weight:7.0%-11.0% Al, 0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Yand a balance of Mg and unavoidable impurities.
 2. The alloy accordingto claim 0 wherein: a content of said Mn is between about 0.15 wt % to0.3 wt % of said alloy.
 3. The alloy according to claim 0 wherein: acontent of said Zn is between about 0.1 wt % to 0.35 wt % of said alloy.4. The alloy according to claim 0 wherein: a content of said Zn isbetween about 0.4 wt % to 0.6 wt % of said alloy.
 5. The alloy accordingto claim 0 wherein: a content of said Al is between about 8.3 wt % to 10wt % of said alloy.
 6. The alloy according to claim 0 wherein: a contentof said Ca and Y is between about 0.75 wt % to 1.5 wt % of said alloy.7. The alloy according to claim 0 wherein: a total combined content ofsaid Al, Ca, and Y does not exceed 11 wt % of said alloy.
 8. An alloyaccording to claim 1 wherein: said Ca and said Y are provided inintermetallic compounds.
 9. The alloy, according to claim 8, whereinsaid intermetallic compounds of Ca and Y comprise: Mg—Al—Ca compoundsand Al—Mn—Y compounds, respectively.
 10. The alloy, according to claim9, wherein: said Mg—Al—Ca intermetallic compound comprises: up of up to57 wt % Al and up to 43 wt % Ca.
 11. The alloy, according to claim 9,wherein: said Al—Mn—Y intermetallic compound comprises 40 wt % Al, 40 wt% Mn and 20 wt % Y.
 12. The alloy according to claim 9 wherein: said Caand Y intermetallic compounds contribute to flammability resistance ofwrought products made from said alloy.
 13. The alloy according to claim0 wherein: said alloy comprises Ca in the form of intermetallicparticles; said particles having an average diameter of about less than1 μm and finely distributed within said alloy.
 14. The alloy, as claimedin claim 13, wherein: said intermetallic particles are formed in awrought process, including extrusion, rolling, or forging.
 15. Thealloy, as claimed in claim 14, wherein: when said alloy is provided in amatrix phase, particles making up said alloy have an average diameter ofabout 10 μm or less.
 16. The alloy according to claim 1 wherein: saidalloy comprises Ca intermetallic particles and said particles make upbetween about 1.0% to 5.0% of said alloy by volume.
 17. The alloy,according to claim 1, wherein: said alloy has a tensile yield strengthof at least 180 MPa and an ultimate tensile strength of at least 270MPa.
 18. The alloy, according to claim 1, wherein: said forged or drawnalloy has a tensile yield strength of at least 170 MPa, an ultimatetensile strength of at least 280 MPa and an elongation of at least 7% intube forms
 19. A method of making a product made from a magnesium-basedalloy composition comprising the steps of: providing magnesium-basedalloy composition comprising, by weight: 7.0%-11.0% Al, 0.1%-0.8% Zn,0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balance of Mg andunavoidable impurities; subjecting said alloy to extrusion whereinbillets of said alloy 1 are hydraulically or mechanically forced throughan orifice in a die to produce an extruded shape; or subjecting saidalloy to rolling wherein billets of said alloy 1 are successively passedthrough rollers to produce a rolled sheet, plate, or simple shape; orsubjecting said alloy to forging wherein billets of said alloy 1 areslowly compressed or quickly impacted with hammers or dies to produce aforged alloy.
 20. The method, according to claim 19, wherein: saidextrusion step comprises extruding said alloy into seamless tubes viaextrusion of a hollow billet around a mandrel, or into structural tubesvia extrusion of solid billets using porthole dies which split metalflow and subsequently merge the metal around a mandrel to form a hollowshape.
 21. The method, according to claim 19, wherein: said extrudedalloy has a tensile yield strength of at least 180 MPa and an ultimatetensile strength of at least 270 MPa.
 22. The method according to claim19, wherein: said extruded alloy has a tensile yield strength of atleast 170 MPa, an ultimate tensile strength of at least 280 MPa and anelongation of at least 7% in tube forms.
 23. A magnesium-based extrusionalloy composition consisting essentially of, by weight: 7.0%-11.0% Al,0.1%-0.8% Zn, 0.15%-0.65% Mn, 0.6%-1.5% Ca, 0.05%-0.6% Y and a balanceof Mg and unavoidable impurities.